Don't worry about it dude, I almost guarantee you won't be the only "out of demographic" there to watch the film. See if you can find anyone locally to watch it with, you'll feel less self conscious in a group :)

The fact that without the sonic rainboom RD performed as filly, Equestria would've been left to the fate of its villains and would have most likely been destroyed by the end of it, pretty much proves you're wrong.